| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a structure extremely difficult to counterfeit, inexpensive and exactly identifiable and suited to a two-dimensional article like paper in particular by forming an identifying medium form a film made of a piezoelectric material having a characteristic piezoelectric effect and giving an AC electric field to a piezoelectric film so as to judge the authenticity of an object utilizing a piezoelectric effect. SOLUTION: A piezoelectric film 3 as an identifying medium us stuck to the prescribed position of an object 1 such as a card. The film 3 can be e.g. the PVDF film of PZT being a representative inorganic piezoelectric body. The object 1 is set to the slit 5 of an identifier 4 so as to be inserted between electrodes 6 and 7. Then, AC voltage is applied to the electrodes 6 and 7 to give an AC electric field to the film 3. Then, the film 3 is vibrated in accordance with its piezoelectric constant and the frequency and voltage level of AC voltage and generates characteristic sound. This is picked up by a microphone 8, converted to an electric signal and collated with previously stored data to judge its authenticity.</p> |
